This section provides background information related to the present disclosure which is not necessarily prior art.
Thermal conductivity of a polymer composite is governed by filler—matrix compatibility, filler size, shape, their synergetic effects, and the processability apart from filler content. In various macro and microfabrication industries such as heat sink industries and microelectronic products, e.g. light emitting diode (“LED”) manufacture, it has been well known to employ metallic materials for thermal conductivity applications, such as for heat dissipation, for cooling semi-conductor containing devices, e.g. computers, solar panels, and the like. For these applications, such as heat sinks, the metallic material typically is tooled or machined from bulk metals into desired configurations. But such metallic conductive articles are typically very heavy, costly to manufacture and are susceptible to corrosion. Further, the geometries of machined metal heat dissipating devices are very limited to the inherent limitations associated with machining or tooling techniques. With respect to microelectronic devices, they too may require heat dissipation in order to provide functional semi-conducting processes. The trend to miniaturize various electronic components requires that heat sink components follow such miniaturization trends to provide aesthetic appeal of certain smaller form factors. Because of the smaller dimensions of the packaging, the heat dissipation characteristics of small microelectronic devices are degraded, which, in turn, may lead to the degradation of the device's performance, erratic behavior, a shortened life span, and other possible undesirable consequences. Many applications also require thermally conducting and electrically insulating applications for which metals are not suitable.
To address the above problems associated with the use of metallic machined parts used for thermal dissipation, attempts have been made to provide molded compositions that include a conductive filler therein to provide the necessary thermal conductivity function. Since the filler binder portion of the composite material is generally non-conductive, there have been problems associated with providing composite materials having a high percentage of filler particles such as greater than 55% by volume, due to reasons primarily associated with filler aggregation.
In thermally-conductive polymer composites, high thermal conductivity values greater than 10 Watts per meter Kelvin (W/m·K) can be achieved typically at higher loadings greater than 60 percent of fillers. Lack of suitable fillers, their synergetic effects and processability, limit the thermal conductivity of the commercially available polymer composites known to date to less than 20 Watts per meter Kelvin. The inventors hereof have recognized a need for moldable thermally-conductive composite materials that exhibit thermal conductivity higher than 20 Watts per meter Kelvin while being easily moldable, including injection molding, for complex and miniature geometries while being relatively low in cost to manufacture.